The commercialization of any chemical compound for use as a pharmaceutical agent requires careful consideration of the formulation in which the chemical compound will be prepared, packaged and stored. The formulation must, of course, be compatible with human and/or veterinary administration. The formulation must be such that the agent retains potency for an extended period of time. Indeed, the formulation itself must be stable over a long period of time. The formulation must be compatible with techniques used for its purification, as well as for the purification of the agent contained within the formulation. Ultimately, the formulation must be compatible with the material in which the agent will be stored. If the agent must be frozen for stability, it is preferable that the formulation provide some protection against inactivation or denaturation due to freeze-thaw. In addition, the formulation should provide a suitable milieu for various dilutions of the agent.
Typically, pharmaceutical agents are stored as lyophilized formulations in a sterile container. A pharmaceutical agent formulation may be lyophilized if it is stable in such a nonaqueous state. This is of particular importance if the formulation must be stored frozen, as lyophilization minimizes the deleterious sequelae that may occur when an aqueous preparation is frozen and subsequently thawed. A glass vial is typically used because of the compatibility of glass with presently used sterilization techniques.
Adeno-associated virus (AAV) is a virus that readily transduces many human tissue and cell types. Accordingly, AAV has been used for gene therapy and nucleic acid immunization. The use of AAV in these contexts requires consideration of the above pharmaceutical formulation requirements. For example, it would be preferred that an AAV-containing sample not be lyophilized because of the possibility that small amounts of virus could become aerosolized and inadvertently transduce an unintended host. However, because AAV is known to be stable under a variety of conditions that would inactivate most viruses, particularly enveloped viruses, it was not previously believed that the preparation of AAV formulations would be problematic.
It was unexpected, therefore, to find that the activity of recombinant AAV (rAAV) virions dropped significantly depending on the formulation used for storage and the conditions to which the formulation was exposed. It has been found, for example, that the transduction activity of a rAAV formulation may depend on the nature of the container, the constituents of the formulation, the temperature of the formulation, as well as changes in temperature, and the concentration of the rAAV virions stored.
It would, therefore, be a significant advancement in the art to provide formulations for storing rAAV virions which would preserve the activity of the rAAV virions for extended periods of times in containers made of various materials, including glass.